Process of separating nitrates of potassium and sodium



OFFICE.

ROBERT P. CALVERT. or WILMINGTON, DELAWARE, ASSIGNOR To E. I. nu PONT DENEMOURS AND COMPANY, OF WILM DELAWARE.

INGTON, DELAWARE, A CORPORATION OF PROCESS OF SEPARATING NITRATES 0FPOTASSIUM AND SODIUM.

No Drawing.

T 0 all whom it may concern:

Be it known that I, ROBERT P. CALVERT, of l-Vilmin ton, in the county ofNew Castle and in the tate of Delaware, have invented a certain new anduseful Improvement in Processes of Separating Nitrates of Potassium andSodium, and do hereby declare that the following is a full, clear, andexact description thereof.

My invention relates particularly to a process for obtaining potassiumnitrate from mixtures of the same with sodium nitrate.

The object of my invention is to provide an advantageous process bymeans of which potassium nitrate may be obtained from mixtures of thesame with sodium. nitrate which mixtures may contain other constituents.More particularly, the object of my invention is to provide a process bymeans of which mixtures of potassium and sodium nitrates, andparticularlysuch mixtures containing from 20 to 40% of potassium nitratemay be treated, so as to effectively separate the potassium nitrate fromthe sodium nitrate. A further object is to bring about thisseparationwithout necessitating the decomposition of the constituents. Afurther object is to bring aboutthe separation of potassium and sodiumnitrates by treating the same at a low temperature, atwhich saidnitrates have different degrees of solubility in water. A further objectis to make use of the mother liquor produced in the process so as toseparate the constituents therein and thus bring about the use of acontinuous process while, at the same time, avoiding waste of thematerials treated. Further objects of my invention will appear from thedetailed description thereof contained hereinafter.

\Vhile my invention is capable of being carried out in many differentways, for the purpose of illustration I shall describe only certainmodes of procedure by means of which my invention may be conducted. Forexample, I may proceed as follows:

A mixture containing from 20 to 40% potassium nitrate and to 75% sodiumnitrate, and which may contain also other constituents as, for example,small proportions of boric acid, calcium sulfate, potassium perchlorate,sodium chlorid, magnesium chlorid, insoluble materials, etc., is

Specification of Letters fatent.

treated with a quantity of water sufiicient to dissolve substantiallyall of the sodium nitrate and, for example, for this purpose, I may add100 parts of such, mixture of nitrates to 80 parts of Water. Thereafterrefrigeration is applied, which may be by means of the application ofice, cold brine, ammonia, etc. Any desired lower temperatures may thusbe obtained, but by way of' example, I may lower the temperature in thismanner to 5 C., or preferably to 15 C. lVhen the desired temperature hasbeen reached the liquid is separated from the crystals by gravity,pressure filtration, or centrifuging. The crystals thus obtained willcontain from 40 to 100% potassium nitrate. In this way a product isobtained containing a very high percentage of potassium nitrate. Ifdesired, this may be subjected to repeated recrystallization to increasethe purity of the potassium nitrate. Furthermore, if desired, the boricacid may be removed by dissolving the potassium nitrate in water, addinglime, and filtering through a pressure filter. This is preferably donebefore the first recrystallization. Instead ofapplying water to themixed nitrates, as above indicated, the process may be carried out bytreating mixed nitrates already dissolved in water in which case therefrigeration is applied to the solution either directly or afterdilution with Water to give the desired concentration. The amount ofwater present affects the percentage of the total potassium nitrateobtained by the cooling. In the case where it is desired to treat asolution of mixed nitrates in which the percentage' of sodium nitrate islarger than that I above referred to, it is desirable to decreasePatented Oct. 26, 1920.

Application filed August 1, 1917. Serial No. 183,825.

tion containing five to six parts of sodium nitrate, and one part ofpotassium nitrate is to be treated, I evaporate the solution until itreaches the density of 54 B., whereupon the solution is allowed to coolto 25 C. and the deposited crystals of sodium. nitrate are then removed.The mother liquor is then subjected to the refrigeration as abovedescribed.

After the refrigeration has been carried out, according to the abovemethods, the mother liquor will contain sodium nitrate and potassiumnitrate in the proportions of 5.7 to 1. This mother liquor may,therefore, be concentrated to a density of 54 B. and then allowed. tocool to 25 C, in the same way that the high sodium nitrate and low potassium nitrate solution, above referred to was treated, thus depositingcrystals of sodium nitrate and leaving a solution containing sodiumnitrate and potassium nitrate in the proportions of approximately 3to 1. Inasmuch as the mother liquor thus remaining contains potassiumnitrate and sodium nitrate in substantially the same proportions as themixed nitrates or solution thereof initially treated by the process asabove described, I may add this mother liquor to a quantity of the mixednitrates solution as initially treated, and then subject the samesimultaneously to refrigeration to bring about a separation of thesodium nitrate from the potassium nitrate in the manner described abovein detail. The mother liquor obtained from this separation may be usedover again in the same way. In this manner any loss of the substancespresent in the mother liquor is avoided, thus making the process acontinuous one.

While I have described my invention above in detail, I wish it to beunderstood that many changes may be made therein. Without departing fromthe spirit thereof.

I claim:

1. The process which comprises separating potassium nitrate from amixture of the same with sodium nitrate by utilizing the differences ofsolubility of the same at low temperatures, so as to separate crystalsof potassium nitrate from the mother liquor containing the sodiumnitrate in a larger percentage than the potassium nitrate.

2. The process which comprises separating potassium nitrate from amixture of the same with sodium nitrate by utilizing the differences ofsolubility of the same at a temperature as low as 5 (1, so as toseparate crystals of potassium nitrate from the mother liquor containingsodium nitrate.

3. The process which comprises separating potassium nitrate from amixture of the same with sodium nitrate by utilizing the differences ofsolubility of the same at low temperatures, so as to separate crystalsof potassium nitrate from the mother liquor 5. The process whichcomprises separating potassium nitrate from a mixture of the same withsodium nitrate in which the potassium nitrate is at least 20% of themixture of nitrates present, by utilizing the difi'erences of solubilityof the same at low temperatures, so as to separate crystals of potassiumnitrate from the mother liquor containing the sodium nitrate in a largerpercentage than the potassium nitrate.

6. The process whichcomprises separating' potassium nitrate from amixture of the same with sodium nitrate in which the potassium nitrateis at least 20% of the mixture of nitrates present, by utilizing thedifferences of solubility of the same at a' temperature as low as 5 C.,so as to separate crystals of potassium nitrate from the mother liquorcontaining sodium nitrate.

7. The process which comprises separat ing potassium nitrate from amixture of the same with sodium nitrate in which the potassium nitrateis at least 20% of the mixture of nitrates present, by utilizing thedifferences of solubility of the same at low temperatures, so as toseparate crystals of potassium nitrate from the mother liquor containingthe sodium nitrate in a larger percentage than the potassium nitrate,and then recrystallizing the potassium nitrate.

8. The process which comprises separating potassium nitrate from amixture of the same with sodium nitratein which the potassium nitrate isat least'20% of the mixture of nitrates present, by utilizing thedifferences of solubility of the same at a temperature as low as 5 (3.,so as to separate crystals of potassium nitrate from the mother liquorcontaining sodium nitrate, and then recrystallizing the potassium ni-.trate.

9. The process which comprises separating potassium nitrate from amixture of the same with sodium nitrate in which the potassium nitrateis at least 20% of the mixture of nitrates present, by utilizing thedifferences of solubility of the same at low temperatures, so astoseparate crystals of potassium nitrate from the mother liquor containingsodium nitrate, then concentrating the mother liquor, cooling the sameso as to remove the sodium nitrate to obtain a mother liquor containinga higher percentferences of solubility of the same at a temperature aslow as 5 0., so as to separate crystals of potassium nitrate from themother liquor containing sodium nitrate, then concentrating the motherliquor, cooling the same so as to remove the sodium nitrate to obtain amother liquor containing a higher percentage of potassium nitrate, thenadding thereto a fresh quantity of mixed nitrates of substantially theabove mentioned proportions and cooling the same in a similar manner toseparate potassium nitrate crystals'from the remaining mother liquor.

11. The process which comprises separating potassium nitrate from amixture of the same with sodium nitrate in which the po-,

tassium nitrate isat least-20% of the mix:

ture ofnitrates present, by utilizing the dif 1 ferences in solubilityof the same at temperatures as low as 5 (3., so'asvto separate crystalsof potassium nitrate from the mother liquor containing sodium nitrate,then concentrating the mother liquor v and allowing the same to cool #toan intermediate temperature so as to separate out the sodium nitratetherefrom by cooling.

12. The process which comprises separat-- ing potassium nitrate, from amixtureof the same with "sodium nitrate in which the 130- tassiumnitrate is at least 20% oi the mixture of nitrates present, by utilizingthe differences of solubility of the same at temperatures as low as 5(3., so as'to separate crystals of potassium nitrate from the motherliquor containing sodium nitrate, then concentrating the mother liquorand allowing the same to cool so as to-separate out the sodium nitratetherefrom by cooling to an intermediate temperature, and

then depositing potassium nitrate therefrom by again cooling to thelower temper-' ature mentioned.

13. The process which comprises concern trating a solution of mixedalkaline nitrates containing sodium nitrate together with less than 20%of potassium nitrate, coo'ling'sut" ficiently to crystallize out somuch' of the sodium nitrate as to "leave a liquor containing above 20%of the nitrate content in the form of potassium-nitrate, separating thesodium nitrate socryst allized, and

then cooling the residual liquor to a temperature so low as tocrystallize out comparatively pure potassium nitrate.

Intestimony thatI. laim the foregoing I have hereunto set m hand: a

I I RO ERT P. CALVERT. Witnesses: 't

' GEORGE D. HOPKINS, Cnn'ris CAL IN COOPER,

